Today's telecommunication networks support a number of different services and, in fact, consist of a number of networks which are interconnected, such as Public Services Telephone Network (PSTN), various mobile or cellular networks, such as the GSM and NMT networks, and data communications networks, for example TCP/IP networks, such as the Internet.
An individual user may be reached on a number of different terminals, depending on the time of day and the type of service desired. For example, a user may typically be reached at a telephone in a business network at work, at a PSTN telephone at home and at a mobile telephone that is switched on only part of the time. At any time, the user can receive telefax on his personal number. The fax will be routed to a telefax machine in accordance with the user's temporary or permanent fax number.
It is possible to let the same, personal telephone number identify all the terminals to which one subscriber is connected. The problem then arises of routing incoming calls to the appropriate terminal.
U.S. Pat. No. 5,490,210 discloses a solution to the problem of automatically selecting a telephone or a telefax machine. A programmable interface device comprising a microprocessor is connected to a subscriber line. The microprocessor receives and interprets digital signals in the incoming traffic and controls the equipment connected to the interface device in dependence of the type of traffic. If the registered Dual Tone Multi Frequency (DTMF) signal indicates a telefax, the call is automatically connected to the telefax machine, if not, the call is connected to a telephone or an answering machine.
U.S. Pat. No. 5,497,373 describes a flexible interface which automatically performs protocol conversion between different types of traffic, such as voice mail, telefax, e-mail, DTMF tone detection, and so on.
None of these patents describe the possibility of manually routing an incoming call to the appropriate terminal. U.S. Pat. No. 5,490,210 also only describes the selection of two kinds of traffic: voice and telefax.
Manually routing an incoming call in many cases is a more flexible solution than automatic routing. Any kind of traffic may be handled, and terminals may be added or changed. Incoming calls may be handled in dependence of the momentary situation in a more flexible way than automatic routing will allow.